Reciprocating piston devices such as pumps, compressors, and internal combustion engines have utilized a single piece direct connecting rod, that is, a fixed length connecting rod between a crank shaft and the reciprocating piston. The result of this use of long connecting rods was a pump, compressor, or engine having an overall axial dimension sufficient to accomodate the necessary motion of the long connecting rod.
While this invention is not restricted to oil less pumps, the prior art of such pumps includes not only reciprocating pistons as described above, but also sliding vane rotary pumps. The sliding vane rotary pump, and also sliding vane rotary compressors, all require an extensive lubrication system to insure that the sliding vanes are maintained in an adequate lubrication environment. This requirement for lubricating the sliding vanes made necessary the use of complicated lubricating systems or materials having self-lubricating properties. Both solutions to the lubrication problem were costly and in addition there are difficulties in maintaining workable pumps or compressors.
While the lubrication of a reciprocating piston type pump, compressor, or other device is well understood, the size requirement necessitated by the use of a fixed length connecting rod prohibited the universal acceptance of reciprocating piston devices where size is a factor.